System for measuring contact rebounding



July 17, 1928 SYSTEM FOR MEASURING CONTACT REBOUNDING Filed Feb. 25, 1925 AA I i 4;

5' 20 :JVo chatter a i l a; 20 5O 40 5 I 5 116W I 5 i s 25 b b g I l I l INVENTOR BY W ATTORNEY Patented July 17, 1923; UNITED STATES PATENT OFFICE. D

ALLAN WEAVER, OF BROOKLYN, NEW YORK, ASSIGNOB TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A OORFOBATION OF NEW YORK.

SYSTEM FOR unasunme CONTACT nnnouunme. Application fled February as, 1925. Serial no. 1am.

This invention relates to methods of and at a given frequency, say, 16 cycles. Whil means for measuring the number of rethe contact is open, the condenser 3 isbounds of contacts, and more particularly charged to the potential of battery 4. Upon the so-called chatter of relay contacts. the operation of the relay and the closing When a relay operates, the armature has of the contact at 2, the condenser 3 will disaa a tendency to rebound, due to such causes as charge through the resistance 5. The resultresiliency, velocity, etc. In the common ing current impulse is represented by the language of the art this rebounding 1s curve 20 of Figs. 2 and 3. If there is no termed chatter. As will be readily unchatter, that is, no rebounding, of the armaderstood, each rebound or chatter has practure 1, the contact will be opened again oneat tically the same efiect upon the contacts of half period later, and the battery 4 will a telegraph relay, for instance, as an addicharge the condenser 3 through the resisttional operation of the relay. In designing ances 5 and 6. This charging current is relay armatures and contacts and in comrepresented by the curve 60 of Fig. 2. On

paring the operation of relays, to take two the other hand, if there are three chatters, 2e

examples, it is of importance that the the current mpulses will be as shown in measure of the chatter or, in other words, Fig. 3, represented by the curves 20, 25, 30,

the number of the rebounds upon a single 35, 4Q, 45, 50, and 55, as will be more fully operation of the relay be ascertained. Hereexplained below.

go tofore, the oscillograph method has been the There is included in the system as a recti- 75 standard method employed for taking simfier and amplifier a thermionic vacuum tube ilar measurements. with rid 7, filament 8, and plate 9. The

Applicants invention provides a method grid, lament, and plate batteries are shown of measuring thenumber ofrebounds which at 10, 11, and 12, respectively. The poling ,5 is superior to the oscillograph method in of the grid battery 10, the plate battery 12, that the ease of operation is greater and the and the battery 4, referred to above, is to be speed of operation increased, and in that noted. A ballistic galvanometer 13 is inchatters of higher frequencies can be cluded in the plate circuit. measured with accuracy. Due to the poling of the battery 10, there Applicants device consists broadl "ofeleczis normally impressed upon the grid 7 a negs5 trical means for accomplishing t e autoative potential. As will be well understood matic registration upon a suitable indicating by those skilled in the art, given this nordevice of the number of rebounds of two mally negative potential on the grid, the contacts when the same are brought together added application of a negative potential to in the operation of a relay or other device. the grid will have no effect on the plate cir- 90 The invention will be clearly understood cuit, whereas the a plication of a positive from the following detailed description of potential to thegri will produce a current one desirable form of applicants device and impulse in the plate circuit, in which is inthe operation thereof when the same is read cluded the ballistic galvanometer 13.

with reference to the accompanying draw- Upon the closing of the relay contact and a ing. Figure 1 of the drawing is a circuit the discharge of the condenser 3, the current diagram of the chatter meter; Fig. 2 repreimpulse through the resistance 5 causes a sents diagrammatically the current impulses positive potential to be applied to the grid occurring in the circuit upon the operation 7, which in turn produces a current impulse of. the relay without chatter; and Fig. 3 through the galvanometer 13 in the plate 1 0 represents in like manner the current imcircuit. When the contact opens, the conpulses produced in the circuit by an operadenser-charging current through resistance tion followed by three chatters of the con- 5 causes a negative potential to be impressed tacts. upon the grid 7. As stated above and as With reference to the details of the drawwill be understood from an examination of 105 ing, the armature 1 is shown in theclosed the poling of battery 10 in Fig. 1 of the position of the circuit, making contact at 2, drawing, this negative potential on the grid and the dotted line indicates the position will not produce a current impulse in the of the armature when the contact 1s open. plate circuit and the galvanometer, since the Let it be assumed that the relay is operated grid is already made sufficiently negative by 119 case, and so on.

the battery 10 to prevent any current in the plate circuit.

From the above description and explanation it is readily understood that the ballistic galvanometer 13 receives a current impulse each time the contact closes and no current impulse when the contact opens. Since the deflection of the galvanometer needle will be proportional to the number of impulses through the instrument and since there is one impulse in the plate circuit to each closing of the contact, it follows that the deflect-ion of the galvanometer needle will likewise be proportional to the number of times the contact closes.

1 If there is no chatter of the relay contact, that is, no rebounding of the armature, the galvanometer will receive one impulse per cycle of relay operation and will show a certain deflection, the amount of this deflection depending upon the frequency of oper-:

ation of the relay. If, however, the relay chatters once, this chatter or rebounding being equivalent to a second operation of the relay, the deflection of the galvanometer. will be twice as great as in the case of no chatter. Likewise, if there are two chatters or rebounds, the deflection of the galvanometer will be three times as great as in the first Accordingly, the number of chatters may be ascertained by taking the observed deflection, dividing this deflection by the amount of deflection corresponding to the base frequency, and subtracting 1. More specifically, given the base frequency of 16 cycles, assumed above, and a corresponding galvanometer needle deflection of :11, if the relay chatters three times, the number of chatters will be ascertained by the use of the following equation, in which C is the number of chatters and D is the total observed deflection:

Since, as explained above, D will be proportional to the number of times the contact closes, D must, given a deflection a: corresponding to the base frequency, be equal to 4m. Therefore, substituting ,in the above equation, we have or the number of chatters.

Unsteady reading on the galvanometer will indicate a variable amount of chatter, and steady reading will indicate systematic chatter.

It will be understood, of course, that the values of the condenser and the resistances in the. circuit should "be chosen so that the time of charging or discharging of the condenser will be shorter than the time during which the contact is open upon the fastest chatter to be'observed.

Applicant does not limit himself to the form of system, described in' detail above, nor to the specific use of his meter explained above, but claims as his invention the following:

What is claimed is:

1. As a means for measuring the number of rebounds of contacts, a system comprising athermionic vacuum tube, a ballistic galvanometer included in the plate circuit of said thermionic vacuum tube, and circuit arrangements whereby each closing of the contacts produces a current impulse in said plate circuit and an opening of the contacts has no efl'ect on said plate circuit.

2. A system for measuring the number of rebounds of contacts, said system com rising a thermionic vacuum tube, a ba istic galvanometer included in the plate circuit of said thermionic vacuum tube, means vanometer in theplate circuit of said ther mionic vacuum tube, a source of energy so poled as to impress a normalnegative potential on the grid of said thermionic vacuum tube, means for impressing a positive potential on said grid in response to each closing of the contacts, said positive potential producing a current impulse in the plate circuit of the therminoic vacuum tube and the ballistic galvanometer included therein, and means for preventing the affecting of the plate circuit upon the opening of the contacts.

4. As means for measuring the number of rebounds of contacts, a network comprising a battery, a condenser, and a plurality of resistance elements; a thermionic vacuum tube comprising a grid circuit, a plate circuit, and a filament circuit; a battery in said grid circuit so poled as normally to impress a negative potential on the grid; an a ballistic galvanometer included in said plate circuit said network being so associated with the contacts and with the grid circuit that the opening of the contacts eter included therein.

5. The method of measuring the number of rebounds of contacts which consists in tacts to disc accumulating a quantity of electrical energy, causin the initial closing of the conarge said energy to produce a basic indication, causing subsequent closing of the contacts to produce an indication readily comparable with said basic indication, and comparing the basic indication with the indication subsequently produced.

6. The method of measuring the number of rebounds of contacts which consists in accumulating a quantity of electrical energy, discharging said'energy in response to the initial closing of the contacts, causing the energy so dischar ed to produce a basic indication, re-accumu ating the quantity of electrical energy each time the contacts reopen, discharging the accumulated energy in response to each re-closing of the contacts, causing the discharged energy to render the indication cumulescent, and observing the relation between the final indication and the basic indication. y

In testimony whereof, I have signed my name to this specification this 21st day of February 1925.

ALLAN WEAVER. 

